The invention relates to parts made of composite material comprising a solid body together with at least one platform present at one of its ends. Such parts relate particularly, but not exclusively, to turbine engine vanes having incorporated inside and/or outside platforms for a turbine nozzle or for a compressor guide vane set.
Document WO 2013/079860 describes making a turbine engine vane out of composite material having inside and outside platforms integrated therein.
As shown in FIG. 14, a vane with inside and outside platforms integrated therein is made from a fiber blank 500 obtained by three-dimensional (3D) for multilayer weaving, e.g. using yarns of silicon carbide fibers or of carbon fibers. The blank 500 has a portion 510 that is to form the airfoil of the vane and in which all of the yarn layers are interlinked. The fiber blank also includes regions of non-interlinking to provide pairs of portions 511 and 512 at each of its ends. As shown in FIG. 15, the inner and outer platforms can be made by deploying those portions 511 and 512 perpendicularly to the portion 510 that is to form the vane airfoil. The preform as obtained in this way is then densified in known manner with a matrix, e.g. a matrix that is made of a material that is ceramic, an oxide, or organic (thermoplastic, thermosetting, . . . ).
Once the portions 511 and 512 have been deployed, a groove or hollow 513 appears between the two deployed portions 511 and 512. If it is not filled in, the groove 513 can create a zone of weakness that can lead to fibers breaking when the part is stressed mechanically. The groove may be filled in by fitting a filler element that may comprise resin on its own or else fiber reinforcement (braid, roving, etc.) impregnated with resin.
Nevertheless, although filling-in in that way serves to improve the mechanical strength of the vane in the zone where the two platform portions separate, it nevertheless presents certain drawbacks. Specifically, adding a fitted filler element makes fabrication of the part more complex since it adds operations additional to those of fabricating the part proper (secondary operations for forming and inserting the filler element on the part that is to be fabricated). This leads to a higher fabrication cost for the part. In addition, although adding such a filler element does indeed serve to improve the compression strength of the part, its traction strength nevertheless remains problematic since the radii presented by the platform portions where they join the airfoil portion of the vane are deformed under traction stresses, which can lead to losses of cohesion and to detachment of the filler element from the remainder of the vane.